Process for the production and recovery of metals in finely divided form



' Patented @ct.28,19i24.

I 1 ,1 WALTER A. SGHMIDT, OF LOS ANGELES, CALIFORNIA, ASSIGNOR '10 INTIEINATIONAL rnncrrrra'rron 0011mm, LOS A GELES, cnmronum, A conrona'rron orcause PROCESS FOR THE PRODUCTION AND RECOVERY OI METALS INFINELY DIVIDED FORM.

E'o Drawing.

and Recovery of -Metals in Finely Divided Form, t which the following is a specification. i

This invention relates to the production of metals in finely divided or pulverulent form, as, for example, the production of zinc powder, flour or dust for use as aprecipitant in metallurgy, or for other purposes, the main object of the invention being to provide for the production of'zinc dust, or other metallic powder, in an extremely fine state of division.

My process may be carriedout as follows:

A molten bath, or body of metallic zinc, or other metal, is raised to a temperature sufliciently high to cause v0latil1zation, sucli operation being conducted in any suitable type of furnace, or retort out of contact c with atmospheric air, so as to. revent oxidation of the metal, for-'examp e, the operation may be conducted in-a furnace of the crucible type, or mufiie type, or of the revereo' beratory type.

- The zinc, or other-metal, volatilized in this manner as metallic vapor is conducted away from the "retort and chilled or cooled in such manner as to produce a fume of as solid metal particles, t e temperature being lowered suflieiently to. cause the separate particles to solidify while still in the form of fume d the resulting fume is collected in thefi; of an'impalpable powan der or dust by an a'mple, by electrical precipitation.

- The metallic vapor may pass from the retort in which it is volatilized by reason of the expansive action of its own vapor pressure (the retort containing the melted zinc being externally heated), or, if desired, a more ra' id volatilization may be efiected by supp ying an inert carrier gas, consist- 'ing, for example, of products of combustion,

so or nitrogen, ora reducing gas, such as hydrocarbpn gas or vapor such carrier gas or vapor being forced or drawn through the,

pended desired means, for exgen, carbon dioxide, or other gas Application died march 10, 1921. Serial No. 451,157.

retort or iurnace so as to carry ofi' the volatilized zinc, or other metallic vapor, more rapidly and increase the rate of volatiliza tion. Such carrier gas may also be utilized as a means for supplying part or all of the required heat to thebody of zinc, or other metal, to be volatilized. For example, the carrier gas may consist of hot products of combustion taking place in the-volatilizing retort, or in a separate combpstion chamber, or such hot gases may be preheated in any other suitable manner. In case products of combustion are used the same will not be completely inert, but will have someoxidizing efi'ect due to the presence of carbon dioxide'and of more or less unbound oxygen, but it has been found in practice that the presence of a small amount of oxidizing gases is not inimical to the process and in some cases, particularly in the production of zinc powder for cyanide precipitation, a slight degree of oxidation is desirable, and my invention includes the use of such an approximately inert gas, as well as a completely inert carrier as.

In order to ensure the profuction of the 'zinc, or other meta1, in finely divided form it is necessary to provide for chilling of the vapor below the solidifying point without allowing the particles to come in contact with one another to any consider-able extent while in liquid'condition. For this purpose, it is desirable to cool the .body of gases or vapor passing from the furnace in such manner as to cause the formatlgn of a cloud or fume 'of solid particles susin the gas instead of by cooling the walls of the conduit carrying the gas and thereby causing the metal to condense in liquid form 'on such. walls. Such cooling ofthe'gases or vapo rs carrying the zinc ,or metal vapor may-be efl'ected by-injection of cold gas, or other cooling medium, mto '5 the body of gas or vapor, such cold gas being, for example, an inert g'as,.su'ch as nitrofree from any tendency to react with the zinc under 'the temeprature existing in the condensing r in the fume carrying body of gas o vapor is to produce a ,fog or cloud consisting of finely divided solid particles of zinc or metal suspended in the resulting body of gas and vapor, such cloud or fume being then collected by electrical precipitabody of gas or vapor carrying, the volatih ized zinc. By the recess above described, it am enabled to pro uce zinc dust in the form of an impalpable powder, which by reason of its extremely finely subdivided condition (as compared with that which can be accom-' plished by granulation or atomization) is especially suitable for precipitation of metals in cyanide leaching processes, and for similar purposes.

The process is also applicable to the reduction of other metals in finely divided condition. Thus copper 'or aluminum may be volatihzed, for example, in an electric furnace, the vapor condensed to form a fume, and the fume collected to form a finely dividedmateri'al capable of use as a me-' tallic paint, or for various uses. Copper flour produced in this manner may be used in ma ring dynamo brushes. Aluminum flour so reduced maybe used in making thermit Similarly iron powder may be produced in this manner and used as a precipitant in copper metallurgy, or as a reducing agent for the production of hydrogen from steam, and finely divided nickel produced in the manner above stated may be used as a catalytic agent.

In the production of iron or nickel powder, an electric furnace may be used in effecting the volatilization. By volatilizing different metals in this manner and bringing the vapors thereof together .and condensing the mixed vapors, a fume may be produced and collected consisting of any desired mixture of metals.

In the manufacture of zinc powder, or

other metallic powder, the inert gas used as above described and consisting of products of combustion, carbon monoxide, nitrogen, I

or any other convenient gas, may be circulated in a closed cycle, that is to say a oer tam amount thereof may bepassed through the furnace and the remainder at a lower temperature introduced into the gas stream to chill and condense the vapors, and then through a prcipitator or filter into a gas holder. The gas can be cooled in a cooler placed between the precipitator and the gas holder, or it may be cooled in the gas holder, or between the gas holder and the a paratus in. which the metallic vapor is hi to form fume, said gas holder being the source from which the cold gas is drawn and blown into the furnace and into the gas or vapor varying the volatihzed zinc to chill the same. In case roducts of combustion are used as approximately inert gas for rapid cooling of the metallic vapor carrying gases in order to produce a fine powder, the gas will not be completely inert, but will have, to some extent, an oxidizing property, and my invention includes the use of such an approximately inert or slightly oxidizing gas as a cooling medium.

As a modification of the operation above described, the zinc, or other-metal, may be maintained in molten condition and an inert carrying gas bubbled through the molten bath, so as to carry oil zinc or metallic vapor, which is condensed to form a fume, such fume being collected, as above de scribed.

W'hat ll claim is:

l. The process which consists in heating material containing metallic zinc in a chamber so as to melt and volatilize the zinc, introducing substantially inert gas into said chamber and thereby ejecting the zinc vapor from said chamber so as to increase the rate of volatilization of the zinc, subjecting the gas passing from said chamber and containmg volatihzed zinc to condensing and separating operations to recover zinc therefrom in finely divided condition, and returning residual gas to said chamber in cyclic operation.

' 2. The process as set forth in claim 1, and in which the residual gas is heated before being returned to said chamber.

3, The process which consists in heating material containing metallic zinc so as to melt and volatilize the zinc, withdrawing the vapors of zinc from contact with the said material, introducing into the vapors so Withdrawn an approximately inert gas which is cooler than such vapors to cause condensation of metallic zinc in finely divided condition, separating the finely divided zinc so condensed, cooling residual gases and returning the gases so cooled to contact with fresh portions of zinc vapor for condensation thereof in cyclic operation of the process.

4. The process which consists in heating within a chamber, material containing metallic zinc, passing approximately inert as through sald chamber to eject the zinc ing operations to recover metal therefrom in finel divided condition, and returning resi ual gas to said chamber in cyclic operation.

6. The process as set forth in claim 6, and in which the residual gas is heated before I being returned to said chamber.

7. The process which consists in heating a metal to melt and volatilize the same, withdrawing the volatilized metal from contact withthe melted metal, introducing into the volatilized metal so withdrawn gas 'which is cooler than such volatilized metal,

so as to cause condensation of metal in finely divided condition, separatingthe metal so condensed, cooling residual gas and returning the gas so cooled to contact with fresh portions of volatilized metal for condensa-v tion thereof, in cyclic operation of the process.

8. The process which consists in heating ametal in a chamber to volatilize such metal, passing gas through said chamber to carry off volatilized metal, introducing into the gas leaving said chamber and containing volatilized metal, gas which is cooler than such volatilized metal so as tocause condensation thereof in finely divided condition, separating such condensed metal from the gas, returning a portion 'of the residual gas to said chamber, and cooling another portion of said gas and returning same'to the gas leaving said chamber, in cyclic operation of the process.

In testimony whereof I have hereunto subscribed my'na'me this 24th day of February, 1921 WALTER A. SCHMIDT. 

